With a view to producing a multi-color image by the electrophotography, there have been proposed in the prior art a number of methods and apparatus to be used for the former, which can generally be divided roughly into the following ones. One of these methods is conducted by using a single photosensitive member and by repeating formation of a latent image by an image exposure and a development with a color toner in accordance with the to a transfer member upon each development to effect the color superposition on the transfer member. And, the second method produces a multi-color image by using an apparatus equipped with photosensitive members in a number according to the number of separated colors, by exposing the photosensitive members simultaneously to optical images in individual colors, by developing the latent images formed on the individual photosensitive members with color toners, and by transferring the images sequentially to a transfer member to superpose the colors.
The first method is accompanied by a serious defect that the plural latent image forming and developing steps have to be repeated to take a long time for the image recording operation so that it is remarkably difficult to speed up. On the other hand, the second method is advantageous in the speed because the plural photosensitive members are used in parallel, but is short of practicability because it requires the plural photosensitive members, optical systems and developing means so that its apparatus is complicated and large-sized to raise the production cost. Moreover, both of those two methods are seriously defective in that they find it difficult to register the images being formed and transferred repeatedly several times so that they cannot completely prevent the color misregistration of the image, and in that they find it difficult to adjust the color reproduction and balance.
In order to drastically solve those problems, it is sufficient to record a multi-color image on a single photosensitive member by a single image exposure, but it is the present technical state that such a method is not developed yet.